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IKE keying daemon charon » History » Version 16

Version 15 (Martin Willi, 05.05.2009 15:11) → Version 16/19 (Tobias Brunner, 24.03.2010 11:37)

h1. IKEv2 keying daemon charon

The _charon_ keying daemon was built from scratch to implement the IKEv2 protocol for strongSwan.
It has a fully multi-threaded design to meet todays requirements.

h2. Architecture

<pre>
+---------------------------------+ +----------------------------+
| Credentials | | Backends |
+---------------------------------+ +----------------------------+

+------------+ +-----------+ +------+ +----------+
| receiver | | | | | +------+ | CHILD_SA |
+----+-------+ | Scheduler | | IKE- | | IKE- |--+----------+
| | | | SA |--| SA | | CHILD_SA |
+-------+--+ +-----------+ | | +------+ +----------+
<->| socket | | | Man- |
+-------+--+ +-----------+ | ager | +------+ +----------+
| | | | | | IKE- |--| CHILD_SA |
+----+-------+ | Processor |--------| |--| SA | +----------+
| sender | | | | | +------+
+------------+ +-----------+ +------+

+---------------------------------+ +----------------------------+
| Bus | | Kernel Interface |
+---------------------------------+ +----------------------------+
| | |
+-------------+ +-------------+ V
| File-Logger | | Sys-Logger | //////
+-------------+ +-------------+
</pre>

|Processor |The threading is realized with the help of a thread pool (called processor), which contains a fixed amount of precreated threads. All threads in the daemon originate from the processor. To delegate work to a thread, jobs are queued to the processor for asynchronous execution.|
|Scheduler |The scheduler is responsible to execute timed events. Jobs may be queued to the scheduler to get executed at a defined time (e.g. rekeying). The scheduler does not execute the jobs itself, it queues them to the processor.|
|IKE_SA Manager |The IKE_SA manager manages all IKE_SAs. It further handles the synchronization: Each IKE_SA must be checked out strictly and checked in again after use. The manager guarantees that only one thread may check out a single IKE_SA. This allows us to write the (complex) IKE_SAs routines non-threadsave.|
|IKE_SA |The IKE_SA contain the state and the logic of each IKE_SA and handle the messages.|
|CHILD_SA |The CHILD_SA contains state about an IPsec security association and manages them. An IKE_SA may have multiple CHILD_SAs. Communication to the kernel takes place here through the kernel interface.|
|Kernel Interface |The kernel interface installs IPsec security associations, policies, routes and virtual addresses. It further provides methods to enumerate interfaces and may notify the daemon about state changes at lower layers.|
|Bus |The bus receives signals from the different threads and relays them to interested listeners. Debugging signals, but also important state changes or error messages are sent over the bus.|
|Controller |The controller provides a simple API for plugins to control the daemon (e.g. initiate IKE_SA, close IKE_SA, ...).|
|Backends |Backends are pluggable modules which provide configuration. They have to implement an API which the daemon core uses to get configuration.|
|Credentials |Provides trustchain verification and credential serving using registered plugins.|

h2. Plugins

The daemon loads plugins at startup. These implement the plugin_t interface (source:src/libstrongswan/plugins/plugin.h). Each plugin registers itself at the daemon to hook in functionality.

<pre>
+-------------------------------------+
| charon +---+ +-----+------+
| | | | stroke |
| | | +-----+------+
| +-------------+ | | +-----+------+
| | bus | ----> | p | | smp |
| +-------------+ | l | +-----+------+
| +-------------+ <---- | u | +-----+------+
| | controller | | g | | sql |
| +-------------+ ----> | i | +-----+------+
| +-------------+ | n | +-----+------+
| | credentials | <---- | | | eap_aka |
| +-------------+ | l | +-----+------+
| +-------------+ ----> | o | +-----+------+
| | backends | | a | | eap_sim |
| +-------------+ <---- | d | +-----+------+
| +-------------+ | e | +-----+------+
| | eap | ----> | r | | eap_md5 |
| +-------------+ | | +-----+------+
| | | +-----+------+
| | | |eap_identity|
| +---+ +-----+------+
+-------------------------------------+
</pre>

There is a growing list of available plugins (see source:src/libcharon/plugins): source:src/charon/plugins):

|stroke |The stroke plugin loads credentials from _/etc/ipsec.d_, reads _ipsec.secrets_ and accepts configurations and control commands from ipsec starter.|
|smp |The smp plugin implements the [[SMP]] protocol to control and query the daemon using an XML interface.|
|sql |The sql plugin provides credentials and configurations from a relational database, see [[SQL]].|
|eap_aka |Implements the AKA EAP module implemented completely in software.|
|eap_sim |Implements the SIM EAP module using either a triplet file or a third party card reader library.|
|eap_md5 |Implements the MD5 EAP module (CHAP).|
|eap_gtc |Implements a GTC EAP module to use for PAM authentication.|
|eap_identity |EAP helper module to serve an Identity over EAP before doing EAP authentication.|
|load_tester |Run [[LoadTests]] against self or a remote host.|
|medcli |Reads mediation/mediated connections for a client from a simple database.|
|medsrv |Reads mediation connections for a mediation server from a simple database.|
|nm |NetworkManager configuration and control interface.|
|uci |OpenWRT UCI configuration backend.|
|unit_tester |Simple unit testing framework for charon and libstrongswan.|